Set network

chgrp staff /dev/net/tun
chmod g+rw /dev/net/tun
modprobe tun
echo 'tun' >> /etc/modules
chmod 666 /dev/net/tun

conf tap

tunctl -d tap0
tunctl -u lz -t tap0

Allow internet

iptables -t nat -A POSTROUTING -o ppp0 -j SNAT --to-source 172.20.0.1  # Use your external IP here
echo "1" > /proc/sys/net/ipv4/ip_forward